The present invention relates generally to a reproduction apparatus for a disk-like recording medium and, more particularly, to a reproduction apparatus capable of reducing power dissipation.
Disk-like high density recording media such as an optical disks, CDs (Compact Disks) and mini disks, have recording tracks provided in a spiral form, where information is recorded outwardly starting from the innermost recording track on the disk. A reproduction apparatus for such a disk-like recording medium is equipped with a semiconductor laser which irradiates a laser beam on a target recording track on the disk, and reproduces information by detecting the reflected laser beam.
The reproduction apparatus further comprises a pickup, which focuses the laser beam on the recording track and acquires the reflected light, and a spindle motor which spins the disk. The pickup has a sled capable of moving roughly in the radial direction of the disk, traversing the recording tracks, and a photosensor which is provided on the sled and is slightly movable by an actuator. The photosensor has a laser diode (semiconductor laser). The reproduction apparatus controls the actuator to accomplish tracking servo and focus servo functions. In the tracking servo, the photosensor slightly moves in the radial direction of the disk to irradiate the laser beam on a desired recording track. In the focus servo, the photosensor moves up and down to focus the laser beam on the target recording track. The reproduction apparatus further performs a spindle servo function which controls the spindle motor to rotate the disk at a constant linear velocity.
Access to disk information or irradiation of the laser beam on the target recording track is controlled based on the result of detection of the reflected laser beam according to the movement of the pickup. That is, focus servo, sled servo and tracking servo functions are executed while turning the disk and irradiating the laser beam from the photosensor. At this time, the number of times the laser beam crosses the recording tracks is counted (track counting) based on the result of detection of the reflected laser beam. In accordance with the track counting and position information of the innermost recording track, the sled servo and tracking servo control the irradiation position of the laser beam. Thus, access the disk information, sled servo, tracking servo and focus servo functions and irradiation of the laser beam from the photosensor are performed.
The sled motor, which is used to move the sled, starts rotating when an applied voltage reaches an activation voltage V1 due to a tracking error, as shown in FIG. 1. When a voltage within the hatched areas in FIG. 1 is applied to the sled motor, therefore, the sled motor does not start rotating. Application of such a voltage to the sled motor thus increases power consumption. For a reproduction apparatus which uses a battery as the system power supply, particularly, the battery life becomes shorter.
Accordingly, it is an object of the present invention to provide a reproduction apparatus for a disk-like recording medium having decreased power dissipation.